(1) Field of the Invention
This invention generally relates to molding of plastics and specifically to a method of producing an essentially self-supporting stratiform article, typically a trim panel of the type used in the interior of automotive vehicles such as vertical wall panels including door panels.
(2) Description of the Prior Art
Generally, trim panels for automobiles are composed of a substrate or base layer for mechanical strength and of an outer cover for visual appearance, feel, and/or comfort. Also, the outer cover frequently comprises more than one area with a specific or distinct color, texture, or resilience; for example, one or more vinyl-covered area(s) for resistance against soil and abrasion are combined with one or more, e.g. two to four areas covered with a textile such as carpeting, cloth or velvet, a foamed layer, man-made or natural leather for pleasing appearance, comfort or soil resistance.
Safe and easy placement of segments of cover stock cut in accordance with the surface area(s) that is (are) to be provided with the particular cover layer,andxe2x80x94most importantlyxe2x80x94in close register with one or more selected area(s), presents several problems some of which may need mutually exclusive solutions so as to require some compromise in the balance of properties.
Most of the problems connected therewith tend to be aggravated by the fact that typical trim panels are xe2x80x9cprofiledxe2x80x9d, i.e. not essentially planar but shaped xe2x80x9cthree-dimensionallyxe2x80x9d to some extent so as to have a xe2x80x9cdepthxe2x80x9d dimension in addition to having width and length. For example, protruding arm rests previously made as separate parts for subsequent mounting on a trim panel should be molded integrally with the panel to simplify production, and such arm rests, typically, require a specific surface structure, be it for comfort of use or for visual appearance. Additional problems are encountered when environmental requirements must be met, e.g. regarding disposal or recycling, or when some desired properties of a material defy meeting another requirement, e.g. the desirable toughness of polypropylene contrasted with its adhesive-repellant surface properties. Further, various aspects of the problems involved, such as structural integrity, ease of manufacture and off-set avoidance tend to increase, sometimes geometrically, with the number of the differing cover segments, e.g. more than two and up to eight or even ten.
The art is replete with teachings of methods for making trim panels and the disclosure in U.S. Pat. Nos. 4,781,956, 4,779,390, 4,810,452, 4,830,929 and 4,873,045 is mentioned by way of example representing what applicant feels to be the most pertinent art herein. Yet, the multiplicity of methods proposed previously might be an indication of the fact that no generally satisfactory method has been found up to now, notably when mass production technology is concerned.
Under the invention, a method of producing a stratiform article includes disposing a preformed insert on a first mold portion, the insert having an exposed edge portion; injection molding a thermoplastic polymer into a mold cavity formed by the first mold portion and a second mold portion so that the polymer substantially fills the cavity and covers the exposed edge portion of the insert on its front, back and edge; and allowing the polymer to solidify, thereby forming a substrate that is bonded to the insert and has a recess in which the edge portion of the insert is disposed, wherein the insert covers a portion of an outer surface of the substrate.
Advantageously, because the edge portion is disposed in the recess, rather than being exposed, the edge portion will not mar the visual appearance of the article.
The disposing step may include disposing the insert on the first mold portion such that the insert has an additional exposed edge portion. The injection molding step may then include injection molding the thermoplastic polymer into the mold cavity so that the polymer covers the additional edge portion on its front, back and edge.
In an embodiment described below, the insert comprises a shielding layer and a cover layer. Advantageously, the shielding layer may function as a shrinkage buffer and a permeation barrier between the cover layer and the thermoplastic polymer that is injected into the mold cavity.
Further under the invention, a method of producing an essentially self-supporting stratiform article usable as an interior automotive panel includes disposing a preformed, contoured laminate insert on a first mold portion, the insert including a leather cover layer and having a pair of opposing exposed edge portions; injection molding a thermoplastic polymer into a mold cavity formed by the first mold portion and a second mold portion so that the polymer substantially fills the cavity and covers each exposed edge portion on front, back and side surfaces of each edge portion; and allowing the polymer to solidify, thereby forming a substrate that is bonded to the insert and has a pair of recesses in which the edge portions of the insert are disposed, wherein the insert covers only a portion of an outer surface of the substrate.
While exemplary embodiments of stratiform articles and exemplary methods for making the same are illustrated and disclosed, such disclosure should not be construed to limit the claims. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention.